Still they come, those promising new playwrights at the Royal Court: EV Crowe is another graduate of the Young Writers Programme who touched a nerve or two in her recent playlet about antagonistic policewomen in Charged, the feminist programme of prison plays at the Soho Theatre.

Here, she charts brand new theatrical territory in the rivalrous friendship of two middle-class ten year-olds in a girls’ boarding school. Janey and Mimi talk drab and dirty to each other in the dorm, parents and teachers at a safe distance, participation looming in a wonderfully inappropriate school production of that masterpiece of infantile hysteria and witch-hunting, The Crucible.

Mimi’s the main, presumably autobiographical, character, with her sad isolation exposed by her “ f--- buddy” Janey, the queue at the telephone to ring home, the surprise encounter with a middle-aged school governor in lavatory (nothing too fishy), and her interview with an off-hand, disillusioned teacher.

Director Jeremy Herrin has polished this little gem to near perfection, and Bunny Christie’s design, lividly lit by Malcolm Rippeth, catches exactly the white-tiled misery of the institution, its corridors and noise outside, its bunk beds and smelly lockers and classrooms.

There are one or two extraordinary coups: Mimi and Janey (Maya Gerber and Madison Lygo) compel the outsider Nina (Ellen Hill) – all three actors, and the three with whom they alternate the roles, are stage debutants – to execute a head-stand with her knickers off (discreetly protected from audience view); and the tuck box thrown out the window lands in the next scene right by the teacher (Annette Badland) in a previous time band. This is young persons’ most personal theatre at its very best.